Evaluation of time history distribution characteristics of lightning electromagnetic field in heterogeneous soil

Existing underground lightning electromagnetic field predictive methods are only relevant to conductivity distributions that are homogeneous or layered. In order to expand the scope of application of lightning electromagnetic field computation, the effect of heterogeneous soil conductivity on the electromagnetic field of lightning return is examined in depth. The current distribution in the lightning return channel is characterized by the dual Heidler discharge channel base current and MTLE return model. Using the full-wave finite element approach, a two-dimensional axisymmetric model is created. The time distribution characteristics of the lightning electromagnetic field in a soil with heterogeneous conductivity are evaluated. According to the research, the lightning electromagnetic field's, horizontal electric field, vertical electric field, and azimuthal magnetic field components are negatively, bipolarly, and positively distributed in the subsurface, respectively. The horizontal electric field dominates the subterranean electromagnetic field. The high conductivity of the soil has a significant attenuation effect on the high-frequency components of the lightning electromagnetic field's three electromagnetic components. The initial response of the horizontal electric field of a nonhomogeneous soil is dependent on the conductivity at the surface of soil, followed by a gradual dependence on the conductivity in deeper soil sections. The subsurface distribution of vertical electric and azimuthal magnetic fields tend to stratify in response to a nonhomogeneous drop in soil conductivity.